For getting started at all
Ten minutes is the block for the moment you cannot face the task. Agree to ten minutes, not to the whole job. When the chime goes you can stop with a clear conscience, or keep going if you have found a thread. Either way, the task is no longer untouched.
For small jobs, and what ten will not do
It also fits the jobs that really are small: the two emails you have been avoiding, a quick tidy of your notes, a read-through before a meeting. It is too short for work that needs context, like writing or debugging. Two minutes off follows, and the next block waits for you to press start. When you want more room, the 15-minute and 25-minute timers are one click away.